The present invention relates to a solar collector in which solar energy is transferred into thermal energy of a fluid which is transmitted therefrom to a point of use. This invention relates also to an array of such solar collectors, the solar collector in all cases including a modified plumbing system to facilitate more convenient assembly into an array and to provide balanced fluid flow across the array.
The solar collector generally comprises a flat plate disposed in an enclosure with a transparent face to receive thermal energy. The plate is in thermal contact with conduits for heat transfer fluid, which fluid is heated by thermal energy striking the plate and conducted from the enclosure by transmission of the fluid to a remote point of storage or use.
While such collectors are sometimes schematically shown as if the inlet and outlet for the heat transfer fluid is disposed on a common side of the collector (see for example FIG. 9 of U.S. Pat. No. 4,051,833-Vandament), all known actual collectors and collector arrays are devised with their inlet and outlet openings on opposite sides of each collector so that the heat transfer fluid makes a simple unidirectional pass through the collector. At least one reason for this is to avoid an accumulation of air or vapor in the heat exchange fluid conduit of the collector which might block fluid flow in the collector, rendering it ineffective and susceptible to overheating. Thus, such unidirectional flow within each collector was considered a practical necessity prior to the present invention. But the present invention with bidirectional flow in each collector has now operated for many months with no perceivable malfunctions or problems due to the modified plumbing of the collectors. This result has been found surprising by certain persons familiar with solar energy collectors and collector array systems.
Another problem that presents itself in solar arrays is uniformity of flow through each collector. In most arrays, even flow is dependent on the manifold size and the pressure drop through the collector. Graduated manifolds are often used in an attempt to produce even flow. Even when these solutions are used, purging the air out of the system on initial filling is a requirement in order that air blockage does not occur. The present invention overcomes these shortcomings by providing a controlled back pressure in each collector of the array.
Inasmuch as the present invention depends upon a reduced diameter downflow conduit (or conversely, a high velocity fluid return conduit) within the collector to carry bubbles or vapor collections downward to the outlet in the solar collector of the present invention, the prior art deemed the most relevant is the hydronic heating system art, in which it is known to use high fluid velocity as a means of removing entrained air, and U.S. Pat. No. 4,122,830-Hapgood, wherein a reduced diameter high fluid velocity return conduit is used in a solar collector array for the same purpose. In each case, however, the high velocity conduit is part of the external plumbing to which is connected a plurality of heating or heat collecting elements (namely solar collectors in the Hapgood system). Hapgood in particular does not in any way suggest or imply a possible simplification of the system there described or an improvement over that system by the inclusion of a high velocity downflow conduit within each collector. Rather, considering the other objectives of the Hapgood disclosure, it is clear that Hapgood had in mind only, and might indeed be inferred to be limited to collectors with the inlet and outlet on opposite sides thereof (see Hapgood Claim 1, lines 33 and 34).
A brief preliminary patentability search on the present invention identified the following patents to be of "some interest":
U.S. Pat. No. 3,952,724 PA1 4,051,833 PA1 U.S. Pat. No. 4,027,653 PA1 4,055,163 PA1 U.S. Pat. No. 4,027,821 PA1 4,060,071
This is not to imply that other relevant art is not available or that this search was exhaustive. Moreover, in the opinion of those responsible for this application, these patents are not sufficiently relevant to warrant separate discussion, beyond that above, with respect to patentability of the invention here disclosed and claimed. Nevertheless, copies of all of these patents are submitted for consideration in conjunction with the examination of this application.